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<h2 id="Summary" name="Summary">概述</h2>
<p><code><strong>Math.atan2()</strong></code> 返回其参数比值的反正切值。</p>
<h2 id="Syntax" name="Syntax">语法</h2>
<pre><code class="language-javascript">Math.atan2(<em>y</em>, <em>x</em>) </code></pre>
<h2 id="Parameters" name="Parameters">参数</h2>
<dl>
<dt>
<code>y, x</code></dt>
<dd>
  数值</dd>
</dl>
<h2 id="Description" name="Description">描述</h2>
<p><code>atan2</code> 方法返回一个 -pi 到 pi 之间的数值，表示点 (x, y) 对应的偏移角度。这是一个逆时针角度，以弧度为单位，正X轴和点 (x, y) 与原点连线 之间。注意此函数接受的参数：先传递 y 坐标，然后是 x 坐标。</p>
<p><code>atan2</code> 接受单独的 x 和 y 参数，而 <code>atan</code> 接受两个参数的比值。</p>
<p>由于 <code>atan2</code> 是 <code>Math</code> 的静态方法，所以应该像这样使用：<code>Math.atan2()</code>，而不是作为你创建的 <code>Math</code> 实例的方法。</p>
<h2 id="Examples" name="Examples">示例</h2>
<h3 id="Example:_Using_Math.atan2" name="Example:_Using_Math.atan2">例子：使用 <code>Math.atan2</code></h3>
<pre><code class="language-js">Math.atan2(90, 15) // 1.4056476493802699
Math.atan2(15, 90) // 0.16514867741462683

<code>Math.atan2( ±0, -0 )</code>               // <code>±PI</code>.
<code>Math.atan2( ±0, +0 )</code>               // <code>±0</code>.
<code>Math.atan2( ±0, -x )</code>               // <code>±PI</code> for x &gt; 0.
<code>Math.atan2( ±0, x )</code>                // <code>±0</code> for x &gt; 0.
<code>Math.atan2( </code><code>-y, ±0 )</code>               // -<code>PI/2</code> for y &gt; 0.
<code>Math.atan2( </code><code>y, ±0 )</code>                // <code>PI/2</code> for y &gt; 0.
<code>Math.atan2( ±y, -Infinity )</code>        // <code>±PI</code> for finite y &gt; 0.
<code>Math.atan2( ±y, +Infinity )</code>        // <code>±0</code> for finite y &gt; 0.
<code>Math.atan2( ±Infinity, x )</code>         // <code>±PI/2</code> for finite x.
<code>Math.atan2( ±Infinity, -Infinity )</code> // <code>±3*PI/4</code>.
<code>Math.atan2( ±Infinity, +Infinity )</code> // <code>±PI/4</code>.
</code></pre>
<h2 id="规范">规范</h2>
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<th scope="col">规范版本</th>
<th scope="col">规范状态</th>
<th scope="col">注解</th>
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<td>ECMAScript 1st Edition. Implemented in JavaScript 1.0</td>
<td>Standard</td>
<td>Initial definition.</td>
</tr>
<tr>
<td><a class="external" href="https://www.ecma-international.org/ecma-262/5.1/#sec-15.8.2.5" hreflang="en" lang="en" rel="noopener">ECMAScript 5.1 (ECMA-262)<br/><small lang="zh-CN">Math.atan2</small></a></td>
<td><span class="spec-Standard">Standard</span></td>
<td> </td>
</tr>
<tr>
<td><a class="external" href="https://www.ecma-international.org/ecma-262/6.0/#sec-math.atan2" hreflang="en" lang="en" rel="noopener">ECMAScript 2015 (6th Edition, ECMA-262)<br/><small lang="zh-CN">Math.atan2</small></a></td>
<td><span class="spec-Standard">Standard</span></td>
<td> </td>
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<h2 id="浏览器兼容性">浏览器兼容性</h2>
<p></p><div class="blockIndicator warning"><strong><a class="external" href="https://github.com/mdn/browser-compat-data" rel="noopener">We're converting our compatibility data into a machine-readable JSON format</a></strong>.
            This compatibility table still uses the old format,
            because we haven't yet converted the data it contains.
            <strong><a class="new" href="/zh-CN/docs/MDN/Contribute/Structures/Compatibility_tables" rel="nofollow">Find out how you can help!</a></strong></div>
<div class="htab">
<a id="AutoCompatibilityTable" name="AutoCompatibilityTable"></a>
<ul>
<li class="selected"><a>Desktop</a></li>
<li><a>Mobile</a></li>
</ul>
</div><p></p>
<div id="compat-desktop">
<table class="compat-table">
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<th>Feature</th>
<th>Chrome</th>
<th>Firefox (Gecko)</th>
<th>Internet Explorer</th>
<th>Opera</th>
<th>Safari</th>
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<td>Basic support</td>
<td><span style="color: #888;" title="Please update this with the earliest version of support.">(Yes)</span></td>
<td><span style="color: #888;" title="Please update this with the earliest version of support.">(Yes)</span></td>
<td><span style="color: #888;" title="Please update this with the earliest version of support.">(Yes)</span></td>
<td><span style="color: #888;" title="Please update this with the earliest version of support.">(Yes)</span></td>
<td><span style="color: #888;" title="Please update this with the earliest version of support.">(Yes)</span></td>
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</tbody>
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<div id="compat-mobile">
<table class="compat-table">
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<th>Feature</th>
<th>Android</th>
<th>Chrome for Android</th>
<th>Firefox Mobile (Gecko)</th>
<th>IE Mobile</th>
<th>Opera Mobile</th>
<th>Safari Mobile</th>
</tr>
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<td>Basic support</td>
<td><span style="color: #888;" title="Please update this with the earliest version of support.">(Yes)</span></td>
<td><span style="color: #888;" title="Please update this with the earliest version of support.">(Yes)</span></td>
<td><span style="color: #888;" title="Please update this with the earliest version of support.">(Yes)</span></td>
<td><span style="color: #888;" title="Please update this with the earliest version of support.">(Yes)</span></td>
<td><span style="color: #888;" title="Please update this with the earliest version of support.">(Yes)</span></td>
<td><span style="color: #888;" title="Please update this with the earliest version of support.">(Yes)</span></td>
</tr>
</tbody>
</table>
</div>
<h2 id="See_also" name="See_also">相关链接</h2>
<ul>
<li>The <a href="Reference/Global_Objects/Math" title="Math 是一个内置对象， 它具有数学常数和函数的属性和方法。不是一个函数对象。"><code>Math</code></a> object it belongs to.</li>
<li><a href="Reference/Global_Objects/Math/acos" title="Math.acos() 返回一个数的反余弦值（单位为弧度），即："><code>Math.acos()</code></a></li>
<li><a href="Reference/Global_Objects/Math/asin" title="Math.asin() 方法返回一个数值的反正弦（单位为弧度），即："><code>Math.asin()</code></a></li>
<li><a href="Reference/Global_Objects/Math/atan" title="Math.atan() 函数返回一个数值的反正切（以弧度为单位），即："><code>Math.atan()</code></a></li>
<li><a href="Reference/Global_Objects/Math/cos" title="Math.cos() 函数返回一个数值的余弦值。"><code>Math.cos()</code></a></li>
<li><a href="Reference/Global_Objects/Math/sin" title="Math.sin() 函数返回一个数值的正弦值。"><code>Math.sin()</code></a></li>
<li><a href="Reference/Global_Objects/Math/tan" title="Math.tan() 方法返回一个数值的正切值。"><code>Math.tan()</code></a></li>
</ul>
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